Migration and Survival of Juvenile Bald Eagles from Arizona

Hunt, W. Grainger; Driscoll, Daniel; Mesta, Robert; Barclay, John H.; Jackman, Ronald E.

doi:10.3356/jrr-08-95.1

Cited by 11 publications

(15 citation statements)

References 10 publications

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“…Survival. Mortality rates of raptors between fledging and breeding age can be high, up to 75% for larger eagles and up to 90-95% for smaller falcons (Newton 1979), although recent telemetry studies have revealed lower rates, such as 54% for Bald Eagles (Hunt et al 2009) and 40% for Golden Eagles, 60-65% first-year mortality in Peregrine Falcons, and 66% in Aplomado Falcons (G. Hunt pers. comm.).…”

Section: Discussionmentioning

confidence: 99%

Trial Restoration of the Harpy Eagle, a Large, Long-lived, Tropical Forest Raptor, in Panama and Belize

Watson

McClure

Vargas

et al. 2016

Journal of Raptor Research

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Section: Discussionmentioning

confidence: 99%

Trial Restoration of the Harpy Eagle, a Large, Long-lived, Tropical Forest Raptor, in Panama and Belize

Watson

McClure

Vargas

et al. 2016

Journal of Raptor Research

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“…We assumed that the breeding period was approximately six months in length (35 d incubation, 82 d in nest, 70 d until independence; Buehler ) and that SIs fledged during the following non‐breeding period. We further assumed that SII lasted a minimum of four years (Hunt et al , USFWS ) and that SIIIs remained in SIII (and reproduced) or regressed to SII (and failed to reproduce; Hansen and Hodges ) each year. Equations with differing spans of SII are in Appendix : Part X.…”

Section: Methodsmentioning

confidence: 99%

“…Migration depends on age and location, but eagles tend to return to the same territory year after year (Buehler , Hunt et al , USFWS ). Departure is often more synchronous than arrival (Buehler et al ), but we modeled migrations as grouped events with no mortality and instantaneous transit.…”

Section: Methodsmentioning

confidence: 99%

“…SIs perished or fledged by fall, so

x_{1}

was equal to one. Eagles reached sexual maturity at five years (Hunt et al ), which we defined as the onset of SIII. Successful maturation into SIII required

x_{2}

=1/6.…”

Section: Methodsmentioning

confidence: 99%

“…The algorithm therefore checked candidate sets where stage‐wise values satisfied this criterion. We further narrowed the algorithmic search to the region of the parameter space with (1) fledgling survival between 0.63 (long movements; Wood ) and 1.0 (short movements; Buehler et al , Hunt et al ), (2) fertility between 0 and 1.5 (Bent , Buehler ), (3) the probability of reaching SIII (breeding age) between 0.35 and 0.65, (4) life expectancy >10 yr, and (5) initial conditions of SII being at most 3 × SIII. Detailed explanation is in Appendix : Part II.…”

Section: Methodsmentioning

confidence: 99%

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Using time series data to assess recent population dynamics of Bald Eagles in the northeast United States

et al. 2019

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We explored the use of time series data to study the recent demographics of Bald Eagles in the northeast United States. We merged a stage-structured population matrix model (PMM) into a combinatorial optimization algorithm (COA) to estimate stage-wise abundances, survival rates, and other dynamics of the eagle population from 1990 to 2018. The PMM includes biannual periods (breeding and nonbreeding), density dependence, and stage-wise migration and dispersal. We demonstrated theoretically that the information contained in 17 yr of time series data of the reproductive stage would have contained all the information for the entire population. We then tested the performance of the COA in estimating transient and asymptotic population dynamics using simulated data. Finally, we assessed the COA under differing modeling conditions (without stage-wise dispersal and in the absence of biological assumptions). We found that time series data of the reproductive class, the skeleton of the PMM, and COA are sole ingredients to reliably estimate stage-wise abundances and survival, but additional biological assumptions are helpful in honing precision of the estimates. The algorithm is a tool to assess population dynamics when demographic data are limited to counts of reproductive adults.

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Implications for bird aircraft strike hazard by bald eagles

et al. 2019

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Bald eagle (Haliaeetus leucocephalus) aircraft strikes have increased since 1998 because their populations have recovered to near historical sizes. Their attraction to airfields and their large body size makes them a danger to aircraft and therefore important to airfield managers. However, bald eagle management is complicated by their special protected status and the place they hold in the eyes of the public. To help airfield managers plan monitoring efforts and make informed management decisions, we studied the movements of 32 bald eagles telemetered as nestlings in the Chesapeake Bay, Virginia, USA, 2013-2018. Managers often need to know when fledged eagles are most likely to move enough to encounter airfields near nests. As fledglings aged, they moved progressively farther from the nest and spent more time away from the nest. Twenty-eight days after fledging, eagles spent most of the day (81 AE 10% [95% CI]) near the nest (<500 m) and only 7 AE 7% of the daytime away from the nest (>1 km). By day 55 fledglings ventured beyond 2.5 km from the nest and spent 32 AE 15% the day >1 km away from their nest. Distances moved, however, were influenced by proximity of the nest to water, the salinity of that water, and human population density. Eagles left their natal nests and generally migrated out of the Chesapeake Bay 60.5 AE 7.7 days (4 Aug) after fledging and returned to the Chesapeake Bay approximately 220 days later (Mar-Apr). Eighty-four percent (27 of 32) of the eagles that we tracked encountered 164 airfields across the east coast with 91% of those airfields located within 10 km of the Chesapeake Bay. Encounters with airfields outside the Chesapeake Bay occurred mainly during the first 1.5 years of life, peaking in late fall and early spring. We recorded eagles on Chesapeake Bay airfields during each year, but encounters peaked in April of the first year of the bird's life. April coincides with the height of reported strikes of eagles by aircraft in the region. Our results suggest that eagles fledging from the Chesapeake Bay are an issue for airports near the Chesapeake Bay and for airports across the east coast. Given the continued growth of the population, this issue is likely to continue and grow in significance.

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Migration and Survival of Juvenile Bald Eagles from Arizona

Cited by 11 publications

References 10 publications

Trial Restoration of the Harpy Eagle, a Large, Long-lived, Tropical Forest Raptor, in Panama and Belize

Trial Restoration of the Harpy Eagle, a Large, Long-lived, Tropical Forest Raptor, in Panama and Belize

Using time series data to assess recent population dynamics of Bald Eagles in the northeast United States

Implications for bird aircraft strike hazard by bald eagles

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